In general, a compressor serving to compress refrigerant in a cooling system for a vehicle has been developed in various forms. Such a compressor includes a reciprocating compressor which compresses refrigerant during reciprocation and a rotary compressor which compresses refrigerant during rotation.
Here, the reciprocating compressor includes a crank compressor which transfers driving force of a drive source to a plurality of pistons using a crank, a swash plate compressor which transfers driving force of a drive source to a rotary shaft equipped with a swash plate, and a wobble plate compressor which utilizes a wobble plate, and the rotary compressor includes a vane compressor which utilizes a rotary shaft and a vane and a scroll compressor which utilizes an orbiting scroll and a fixed scroll.
FIG. 1 shows a configuration of a scroll compressor according to the related art. Referring to FIG. 1, the scroll compressor includes a drive portion 20, a compression portion 30, and a control portion 40 which are installed inside a housing 10 defining an external appearance thereof. A space within the housing 10 is divided into a suction chamber 50, a compression chamber 60, a discharge chamber 70, and a back-pressure chamber 80.
The drive portion 20 includes a stator 21 and a rotor 22 which are coaxially mounted inside the housing 10, and a rotary shaft 23 installed therethrough. The compression portion 30 includes a fixed scroll 31 fixed to one side within the housing 10 and an orbiting scroll 32 which defines the compression chamber 60 by engaging with a fixed scroll 31 while being eccentrically rotated by the drive portion 20. In this case, the orbiting scroll 32 is eccentrically coupled to the rotary shaft 23 by an eccentric bush 24.
In addition, the control portion 40 includes a variety of drive circuits and elements such as a PCB mounted inside the housing 10.
The suction chamber 50 is a space in which refrigerant introduced from the outside of the housing 10 is stored. The compression chamber 60 is a space in which refrigerant introduced into the suction chamber 50 is compressed. The discharge chamber 70 is a space to which refrigerant compressed in the compression chamber 60 is discharged. The back-pressure chamber 80 is a space in which a pressure is defined such that the orbiting scroll 32 is pressed toward the fixed scroll 31.
Hereinafter, a description will be given of a process of compressing refrigerant by the scroll compressor having the above-mentioned configuration. First, when external electric power is applied to the control portion 40 through connection terminals or the like, the control portion 40 transmits operation signals to the drive portion 20 through the drive circuits or the like.
When the operation signals are transmitted to the drive portion 20, the stator 21 in the form of an electromagnet, which is press-fitted on an inner peripheral surface of the housing 10, is energized and magnetized, and thus an electromagnetic interaction is generated between the rotor 22 and the stator 21 so that the rotor 22 rotates at high speed.
In this case, when the rotary shaft 23 of the drive portion 20 rotates at a high speed along with the rotor 22, the orbiting scroll 32 of the compression chamber 30 eccentrically coupled to a rear end of the rotary shaft 23 is synchronized therewith and eccentrically rotates at high speed. Consequently, as the orbiting scroll 32 revolves around the fixed scroll 31 with which the orbiting scroll 32 is matched in the form of facing each other, refrigerant flowing from the suction chamber 50 to the compression chamber 60 is compressed to high pressure while being directed from an outer periphery of the scroll to a central portion thereof, and is then discharged to the discharge chamber 70. Accordingly, a series of refrigerant compression operations is completed.
Meanwhile, refrigerant discharged to the discharge chamber 70 is transferred outside the housing 10 and a portion of the refrigerant is transferred to the back-pressure chamber 80. Then, a pressure is generated in the back-pressure chamber 80 by the refrigerant transferred to the back-pressure chamber 80 and the orbiting scroll 32 is pressed toward the fixed scroll 31 by the pressure, thereby enabling the compression chamber 60 to be sealed while the orbiting scroll 32 is pressed against the fixed scroll 31 without a gap therebetween.
Here, a pressure in the back-pressure chamber 80 is regulated in response to a pressure in the suction chamber 50 through a check valve 90 installed in the back-pressure chamber 80. That is, when the pressure in the back-pressure chamber 80 is higher than the pressure in the suction chamber 50 by more than a certain magnitude, the check valve 90 is opened such that refrigerant in the back-pressure chamber 80 is transferred to the suction chamber 50. As a result, the pressure in the back-pressure chamber 80 is maintained to be higher than the pressure in the suction chamber 50 only by the certain magnitude.
This configuration in which the check valve 90 is operated by a pressure differential between the suction chamber 50 and the back-pressure chamber 80 so as to regulate the pressure in the back-pressure chamber 80 is disclosed in Japanese Unexamined Patent Application Publication No. 1998-110688, published on Apr. 28, 1998 (Patent Document 1).
However, in a scroll section of the compression chamber 60 in which a high pressure is defined, a discharge pressure is higher compared to a pressure in the back-pressure chamber 80. Therefore, the orbiting scroll 32 slightly moves toward the back-pressure chamber 80 with the consequence that an inner leak is caused due to a gap generated between the fixed scroll 31 and the orbiting scroll 32.
In addition, in a scroll section of the compression chamber 60 in which a relatively low pressure is defined, the pressure in the back-pressure chamber 80 is higher compared to the discharge pressure. Therefore, the orbiting scroll 32 is excessively pressed toward the fixed scroll 31 with the consequence that electric power is significantly required to drive the orbiting scroll 32.
Moreover, in a case of managing the pressure in the back-pressure chamber 80 in connection with the pressure in the suction chamber 50 as in Patent Document 1, a cross-sectional area of a suction passage and the like are non-uniform in size and temperature of refrigerant is increased by the stator 21 heated to high temperature in the suction chamber 50. Consequently, back-pressure management may be disadvantageous due to an error occurring between a measured suction refrigerant pressure and an actual refrigerant pressure in the suction chamber.